msm: mdss: implement commit ioctl for display commit

Commit ioctl is used to update contents on display while avoiding
console_lock done through framebuffer pan_display path, which causes
additional delay on display pipeline leading to flickers on HDMI.

Change-Id: Id3522d322ba08b110d540e10214cadfbbb0bcc25
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>